


Mommy's Big Boy

by Sidoh



Category: Mystic Messenger (Video Game)
Genre: Age Play, Anal Fingering, F/M, Mommy Kink, Oral Sex, Prostate Massage, Very Mild Medical Kink, sexual age play
Language: English
Status: Completed
Published: 2017-02-11
Updated: 2017-02-11
Packaged: 2018-09-23 14:46:31
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,937
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9661973
Author URL: https://archiveofourown.org/users/Sidoh/pseuds/Sidoh
Summary: Yoosung looks up at you, his violet eyes wide and confused. “I don’t understand, Mommy.”“Well, I do suppose it’s time you knew about these things. I think you might be old enough. You’re Mommy’s big boy, aren’t you?” Yoosung nods vigorously. You pull him close as you start to explain. “When adults love each other, they sometimes like to make each other feel nice.”





	

**Author's Note:**

  * For [vidoxi](https://archiveofourown.org/users/vidoxi/gifts).



> For Vidoxi, who requested Yoosung/MC Mommy kink. I hope this is okay.
> 
> This is a fic of firsts for me. I've hardly ever written anything heterosexual, and I've never written anything in the second person. Also, I'm a big fan of non-sexual age play and have never written sexual age play before. However, I really wanted to give this a shot because I hate how Daddy kink always seems to be the default, and also because it's Yoosung and it makes sense. 
> 
> Speaking of age play: Both characters in this fic are consenting adults. It's roleplay, and no one is having sex with minors or wanting to have sex with minors. Sex with minors is bad.

“Mommy?” 

You’re still half asleep when you hear Yoosung’s voice, and it takes a moment to register what the utterance means. You smile sleepily, effortlessly slipping into your role. “Yes, baby?”

When there is no immediate response, you open your eyes. Yoosung looks at you guiltily, probably worried about having woken you up. “I don’t feel very good,” he finally admits. “I feel all warm.”

“Oh no, sweetie. Do you think you have a fever?” Yoosung does feel hot where he’s pressed up against your body, but that doesn’t say much. You often joke that Yoosung is like your own personal heater at night. “Mommy’s going to get the thermometer, okay? Just wait here.” 

You climb out of bed to retrieve the thermometer from the bathroom cabinet, even though you doubt that Yoosung actually has a fever. A suspiciously high number of Yoosung’s little days have started with him declaring that he isn’t feeling well, and you’re starting to think that he is simply too embarrassed to let you take care of him when he doesn’t have an excuse. You wish he’d believe you when you keep assuring him that you love this side of him just as much as the rest of him. 

“Let’s see,” you say when you return with the thermometer, determined to have a little fun with this. “There’s only one way to take your temperature completely accurately.”

“In my mouth?” Yoosung guesses. 

You shake your head. “No, baby. Up your butt.” You have no idea if this is actually true, but it’s worth the sight of Yoosung’s eyes widening as you pull at the waistband of his underwear. “Come on, lift your bum.”

“But Mommy…” He looks up at you, his eyes pleading. “Does it have to be…”

“Yoosung,” you say a little more sternly. “We have to find out if you have a fever, don’t we? Are you going to be a big boy for Mommy?”

Yoosung hesitates for a moment, but eventually lifts his butt and helps you pull off his briefs. “Good boy,” you say with a smile. You push at the inside of his thighs, encouraging him to spread his legs wider. “Now, this isn’t going to hurt at all if you relax. There’s nothing to be scared of.”

You wet the tip of your index finger with your tongue and massage the ring of muscle around Yoosung’s little hole until it’s relaxed enough to enter. You press the tip of your finger inside ever so slightly, just enough to let him get used to the sensation. Even though the thermometer is more slender than a finger, it’s cold and hard and you figure it might be uncomfortable if he isn’t loose enough. 

As soon as you replace your finger with the thermometer, you realise that Yoosung’s cock isn’t entirely flaccid anymore. You pretend not to notice. “Alright, now we’ve just got to wait for a little bit. It’ll be over before you know it.” Yoosung doesn’t respond, lips clamped together and face red with embarrassment. You might have believed that he's truly uncomfortable if it weren't for the way his cock continues to slowly harden under your gaze. You wonder if his body is responding to the attention his butt is receiving or to the vulnerable and exposed position he’s in.

When the beep comes, it’s no surprise that Yoosung’s temperature is perfectly normal. “Good news,” you say cheerfully as you read the numbers on the tiny screen. “You don’t have a fever.” 

“Oh,” Yoosung responds quietly, sounding almost disappointed. You sigh, putting the thermometer on the bedside table. 

“Yoosung?”

“Yes, Mommy?”

“You know that it’s bad to tell lies, don’t you?” You immediately feel the need to reassure him when you see the worried and slightly guilty look in his eyes. “Mommy loves taking care of you. But that’s why I wish you would tell me when you want something, okay? So be a big boy for Mommy, and use your words.” 

“I’m sorry, Mommy,” Yoosung whispers, avoiding eye contact. “I will use my words.”

“Good boy.” You lean in to kiss him on his forehead. “Because otherwise I might have to punish you. And we already know that you enjoy it when Mommy spanks you, so I would have to put you in time-out instead.” 

Yoosung quickly shakes his head, but you can feel his cock twitching against your stomach at the suggestion of punishment. You have to bite your lip to keep from grinning. “Please don’t, Mommy. I’ll be a good boy and tell you when I want something.” He pauses. “Mommy?”

“Yes?”

“What you did before...” He starts nervously. “It made me feel kind of funny.”

You can’t keep a smile from forming on your face. Ah, so it’s going to be _that_ kind of morning. “A good or bad kind of funny, sweetheart?”

“I don’t know,” he says, a faint blush colouring his cheeks pink. “The thermometer was kind of thin and pointy, but your finger felt nice.”

You reassuringly stroke his hair. “That’s perfectly normal, baby. There’s nothing to be ashamed of. It just means my little boy is growing up.”

He looks up at you, his violet eyes wide and confused. “I don’t understand, Mommy.”

“Well, I do suppose it’s time you knew about these things. I think you might be old enough. You’re Mommy’s big boy, aren’t you?” Yoosung nods vigorously. You pull him close as you start to explain. “When adults love each other, they sometimes like to make each other feel nice.”

“You mean they do nice things for each other?”

“Yes, they do nice things for each other. But they also touch each other in ways that make them feel good. They give each other kisses, like this.” You demonstrate by softly pecking Yoosung on the lips. You let your mouth linger for a while, brushing your lips against his just barely for a moment before you continue to speak. “But if they want to, they can also touch each other in other places. Like how Mommy put her finger inside of you before. Except they do it for a long time until it feels very good.”

“Oh…” Yoosung processes the information for a moment, looking so full of wide-eyed innocence that you almost forget that you’re not telling him anything new. You think you’re slowly starting to understand why it’s easier for Yoosung to be open about sexuality like this. Yoosung is always unnecessarily worried when it comes to sex—worried that he’s not manly enough if he lets you take charge, worried that he’s too inexperienced to please you. Like this, he doesn’t have to be concerned about any of those things because there are no expectations. He gets to hide behind complete innocence, and you’ll never be able to tell the difference even if genuine uncertainty or inexperience shines through. 

“Mommy?”

“What is it, honey?”

He bites his lip. “You...You love me, right?”

“Of course I love you.” You free his bottom lip from the grip of his teeth, gently rubbing the small dents they made with the pad of your thumb. “What makes you ask that?”

“It’s just…” Yoosung looks away. “You said that people make each other feel nice like that when they love each other.”

Your lips curl into a smile as you realise where this is going, relieved that Yoosung isn’t actually questioning your love. “Yes, baby. Do you want Mommy to touch you more?”

Yoosung nods, looking breathless and flustered. “Just to try. If it feels bad…”

“If it doesn’t feel good, just tell Mommy and I’ll stop.” You sit up again and retrieve a bottle of lube out of a drawer next to the bed. “Now be a good boy and relax like you did before,” you tell him as you slick up your fingers. 

Yoosung nods, but you can tell that he’s more tense this time, now that the practical reason for doing this is gone and it’s all sexual. He holds his breath when you slowly circle his hole with your fingertip. Having something even as small as a finger inside of him is still a relatively new feeling for him, and he only lets you do this to him when he’s your little boy. “Breathe for me, baby,” you remind him. “Relax.”

You push your finger inside as soon as Yoosung exhales. He gasps when your finger enters him deeper than before. You experimentally move it inside him, slowly thrusting in and pulling almost all the way out again. “Mommy is going to put in another finger,” you warn him once you think his body can handle it. “Is that alright?”

“Please. Feels good, Mommy.” Yoosung lets out a content little sigh when your first finger is joined by a second. His lips are slightly parted and his eyes are squeezed shut. When you notice the blush on his cheeks, you wonder how he manages to look so innocent and almost shy while putting on such an erotic display. 

When it seems like he’s adjusted to the feeling enough, you stop moving your fingers in and out in straight movements and curl them upward instead, in search of Yoosung’s most sensitive spot. Even before you find it, his ragged breathing is accompanied by little moans as you explore his inner walls. You watch him carefully, paying attention to all of his reactions until your fingers suddenly brush the right place and he cries out, gripping the sheets in his fists. 

“Found it,” you say, unable to stop yourself from feeling a little proud of how Yoosung is writhing under your touch. “Feels good, doesn’t it?” You don’t get a reply, but to be honest, Yoosung’s physical responses and the sounds he’s making tell you more than enough. You locate the spot again and continue to rub and press against it until his cock looks painfully hard and a bead of pre-come drips onto his stomach. “Now what is this?” you ask playfully. 

“I’m....it hurts.” Yoosung opens his eyes and looks straight at you as he adds, “Please, Mommy.” 

Sometimes you’re not sure if he’s really as innocent as he seems or if he knows exactly what he is doing. Right now, as he stares up at you with big puppy eyes while begging so prettily for you to touch him, is one of those moments. If your panties were wet before, they’re soaked now. 

“You want Mommy to kiss the boo-boo better?” You lean in and tease him for just a moment, letting your breath ghost over his erection. When you finally press a kiss to the head, the first contact sends a palpable jolt through his body. You tease him with slow, open-mouthed kisses and a slack tongue, trying to drag this out as long as possible, but along with your fingers still moving inside of him, it doesn’t take long to push Yoosung over the edge. You feel him starting to clench around your fingers just as you finish licking a slow trail from base to tip. 

“Thank you Mommy,” he says when you’re gently cleaning his stomach and penis with a damp washcloth. “That felt really nice.”

“You know why that is? Because Mommy loves you a lot.” You finish wiping the excess lube from between his butt cheeks and smile down at him. You sneak a hand between your thighs, and you can feel just how swollen your clit is through the wet material of your panties. You’re aching to be touched. 

“Hey Yoosung, sweetie?” He looks up at you, unsuspecting. “Do you love Mommy a lot, too?”


End file.
